crystal reports 2011 qr code Structure of a Web Form in C#.NET

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Structure of a Web Form
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The Page object s fully qualified name is System.Web.UI.Page. In the last chapter you saw how this type is an implementation of the IHttpHandler interface, and it simply plugs into the ASP.NET request processing pipeline. Now take a closer look at the object graph of this particular handler, which is shown in Figure 3-1. This object graph applies to Web Forms, as long as you leverage the code-behind model. When no code-behind is used, the code-behind page object is removed from the graph; in this case, the markup contains the code in server-side script blocks. In version 2.0 of the .NET Framework, a new Web Form model that supports a partial classes feature is baked into both C# and VB .NET. Partial classes introduce a number of subtleties into the structure of a Web Form that warrant a closer examination.
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CHAPTER 3 PAGE OBJECT INTERNALS
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Figure 3-1. The Page object s ancestors and descendants (when you re using the code-behind model)
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With partial classes, you have a new approach to building Web Forms that involves a partial class inheriting from the Page base class. One file for the partial class is the code you d normally add to the code-behind. The other file for the partial class isn t created until a run-time compilation step occurs. This is where all of the code that the designer would normally generate during development gets added to the mix. Let s take a look at an example of a page in version 1.x and the changes required to use it in version 2.0. Consider the following markup: <%@ Page language="c#" Codebehind="WebForm1.aspx.cs" Inherits="WebDemo.WebForm1" %> <HTML> <HEAD> <title>WebForm1</title> </HEAD> <body> <form id="Form1" method="post" runat="server"> <asp:Label id="Label3" runat="server">User Name</asp:Label><br> <asp:TextBox id="TextBox1" runat="server" /><br> <asp:Label id="Label2" runat="server">Password</asp:Label><br>
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CHAPTER 3 PAGE OBJECT INTERNALS
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<asp:TextBox id="TextBox3" runat="server" /><br><br> <asp:Button id="Button1" runat="server" Text="Login" /><br> <asp:Label id="lblOutput" runat="server" /> </form> </body> </HTML> In version 2.0, Microsoft has dropped support for the CodeBehind attribute, and, instead, substitutes the new CodeFile attribute. Here s functionally equivalent markup in 2.0. The only difference is CodeFile replaces CodeBehind. <%@ Page language="c#" CodeFile="WebForm1.aspx.cs" Inherits="WebDemo.WebForm1" %> <HTML><HEAD><title>WebForm1</title></HEAD> <body> <form id="Form1" method="post" runat="server"> <asp:Label id="Label3" runat="server">User Name</asp:Label> <asp:TextBox id="TextBox1" runat="server" /> <asp:Label id="Label2" runat="server">Password</asp:Label> <asp:TextBox id="TextBox3" runat="server" /> <asp:Button id="Button1" runat="server" Text="Login" /> <asp:Label id="lblOutput" runat="server" /> </form> </body> </HTML> Realize that version 2.0 does not support the CodeBehind attribute. This is a code breaking change that requires a conversion to move Web Forms from 1.x to 2.0. Considering that most of the changes for 2.0 are backwards compatible and require no changes to work in 2.0, this is worth noting. The code-behind file contains much more significant differences. Here is the 1.x version of the code-behind for the markup we just examined. public class WebForm1 : System.Web.UI.Page { protected System.Web.UI.WebControls.Label Label3; protected System.Web.UI.WebControls.Label Label2; protected System.Web.UI.WebControls.TextBox TextBox3; protected System.Web.UI.WebControls.Button Button1; protected System.Web.UI.WebControls.Label lblOutput; protected System.Web.UI.WebControls.TextBox TextBox1; private void Page_Load(object sender, System.EventArgs e) { // Put user code to initialize the page here }
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CHAPTER 3 PAGE OBJECT INTERNALS
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#region Web Form Designer generated code override protected void OnInit(EventArgs e) { // // CODEGEN: This call is required by the ASP.NET Web Form Designer. // InitializeComponent(); base.OnInit(e); } /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { this.Load +=new EventHandler(Page_Load); } #endregion } Not only is there an entire region of generated code for this very simple Web Form but also the designer generates all of the control declarations that immediately follow the class declaration. This region of generated code, along with the requisite control declarations (as determined by your markup), are what is left out of the version 2.0 code-behind and then added with the second partial class file at runtime (see Figure 3-2). Here s the same code converted to work in 2.0: public partial class WebForm1 : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { } } That s it. Really. Well, this code does nothing! you might say. True, it does nothing. But if you look closely at the version 1.x block of code above, you ll realize that it also does nothing. That s a lot of code to do nothing, isn t it This is the main benefit of using partial classes. It removes a lot of the internal goo code that adds no value to your development experience.
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Note This model changed from Beta 1 to Beta 2. If you ve played around with, or have read up on, the
Framework changes with the PDC Bits, or Beta 1, you ll have a different story for the changes to the page model than the one we present here. People hated the PDC Bits model, so Microsoft changed it with the release of Beta 2. It reverted the model to look much more like the one in version 1.x.
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